[er_ijaz]

Hi
I'm modelling multiple porous zone as concentric rings.

I have following doubts.

My flow is unidirectional along z axis (perpendicular to the concentric rings) and circles are concnetric along y axis

How should I define the directional vector?

Is it necessary to create interface between the porous zones and just leave it as interior?

Do I need to create interface between the normal zone and porous zones?
I'm just calculating the pressure difference across the rings
and calculate inertia and viscous terms (1/alpha and C2)
Do I need to consider any thing other than this

Regards
Ijaz